Integrative study of two invasive North American pine aphids (Cinara atlantica and C. watsoni) in South Korea.

This study investigates the seasonal ecology, morphology, and invasion history of the aphids Cinara atlantica and C. watsoni (Hemiptera: Aphididae: Lachninae) in South Korea and assesses their potential ecological impacts. Historically, C. atlantica was recorded only on non-native pines, but we provide the first evidence of host expansion to the native pine Pinus densiflora. C. watsoni is recorded for the first time in South Korea on imported pines, indicating a potential risk of spread to native hosts. Field surveys conducted between 2020 and 2025, including monthly monitoring, showed that both species reproduce anholocyclically, with colony densities peaking in June and October-November. Honeydew accumulation promoted sooty mold development, and heavy infestations caused needle yellowing. Morphological redescriptions, DNA barcoding, and haplotype analyses confirmed species identities and revealed minimal genetic divergence between South Korean and Nearctic populations. Shared haplotypes with North American material suggest a recent introduction possibly mediated by international plant trade, although the precise source remains uncertain. These findings highlight the high invasion potential of Cinara species and emphasize the need for strengthened phytosanitary measures and continuous monitoring of conifer-associated aphids in East Asia.